Reversing mechanism.



C. H. NORTON.

REVERSING MECHANISM.

APPLICATION FILED NOV. 5, 1915.

Patented July 2-5, 1916.

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C. H. NORTON.

REVERSING MECHANISM.

APPLICATION FILED NOV. 5. 1915.

Patentd July 25, 1916. I

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CHARLES H. NORTON, OF WORCESTER,' MASSACHUSETTS, ASSIGNOR TO NORTON GRINDING COMPANY, OF WORCESTER, MASSACHUSETTS, A CORPORATION OF MASSACHUSETTS.

REVERSING MECHANISM.

Specification of Letters Patent.

Patented July 25, 19 16.

Application filed November 5, 19-15. Serial No. 59,855.

ticularly designed for use in reversing the work table of a modern high duty grinding machine.

The work table in a modern grinding machine is often of large size and great weight and it is moved at a rate of speed which renders the reversal of its travel a very serious problem. The reversal period is necessarily very short and the shock and strain of the reversal is severe. In fact the permissible reversal strain practically de termined the maximum table speed in many grinding machines.

It is the general object of my invention to provide an improved reversing mech anism by means of which a heavy moving work table or other similar object may have its direction of travel at high speed'reversed without shock or undue strain upon the driving or reversing mechanism.

With this general object in view one feature of my invention relates to the provision of mechanism' for effectively reversing a worm and worm wheel drive, the worm at the moment of reversal being given a sliding instead of an angular movement. In the preferred form, the worm is free to move bothaxiallyand angularly upon its driving shaft, suitable provision being made for limiting both the axial and angular movement.

' More specifically my invention relates to the provision, in a worm and worm wheel drive, of a sliding worm having a cam disk secured to each end thereof and coiiperating with rolls carried by a pair of driving arms fixed to the shaft upon which the worm is supported.

Further features of my invention relate to the provision of means for yieldingly retaining the cam disks and driving arms in operative relation while the table is being brought to rest and to the provision of special constructionsin the cam disks for preventing shock to the mechanism during this retarding action.

"ings.

My invention also relates to certain arrangements and combinations of parts which will be hereinafter described and more particularly pointed out in the appended claims.

Preferred forms of my invention are shown in the drawings, in which- Figure 1 is a front elevation of my improved reversing mechanism; Fig. 2 is an enlarged sectional elevation taken through the axis of the driving shaft and showing the driving connections between the shaftand the worm; Fig. 3 is a diagrammatic plan view showing the relations of the cam disks to each other; Fig. 4 is a development of one of the cams; Fig. 5 is a development of a modified form of cam, and Fig. 6 is a sectional elevation of a modified form of my invention. r

Referring to the drawings, I'have shown my improved reversing mechanism as embodied in the table drive of agrinding or.

other similar machine.

The work table is indicated at 10 and is provided with a rack 11 meshing with a pinion 12 fixed to a shaft 13 driven bya worm wheel 14. The worm wheel lat is driven bya worm 15 mounted upon a driving shaft 16 rotatable in bearings 17 and 18 carried by a frame 19. These bearings are preferably of the ball bearing type (as indicated in Fig. 2) and are designed to resist both the radial and the axial thrust of the driving shaft.

F or the purposes of this application the driving shaft may be considered as revolving in fixed bearings and as being re-' strained from axial movement in said bear- Under certain conditions it may be desirable to provide for a slight axial cushioning movement of the shaft, but such provision would not modify or in anyway interfere with the operation of the mechanism herein shown. Any suitable mechanism may be provided for driving the shaft 16 alternately in opposite directions. In Fig. l I have shown a power shaft 20 keyed to a bevel gear 22 having an extended hub rotatable in a fixed bearing 23. The driving shaft 16 is alined with the power shaft 20 and the end of the shaft 16 finds a bearing in the hub of the gear 22. The bevel gear 22 meshes with a second bevel gear 24 rotatable in a bearing 25 in the frame 19, and the bevel gear-24 meshes in turn with a third bevel gear 26 loosely mounted-upon the the shaft 18.

is keyed to the shat 16 and driving shaft 16. A slicing clutch collar 2'? suitable devices (not shown) are provided lor moving the collar 27 alternately into engagement with the beveled gears 22 and iii, thereby period ically reversing the direction of rotation of the shaft 16. The keyvvay in the clutch collar 27 is commonly of such width asto allow a substantial amount of lost motion between the collar 27 and the shaft 16 at each reversal of the collar. The parts thus far described form no part of my invention and may he of any usual or desired type.

I will now describe the novel. driving-connections between the driving shaft 16 and the worm 15. The worm 15 is loosel mounted upon the shaft 16 and is free to move thereon both axially and angularly within certain fixed limits. At its opposite ends the worm is provided with cam disks 30,

and 31 which are securely fixed to the worm to rotate therewith. Each disk is provided with a cam surface upon its outer end face, the cam surface 30 of the disk 30 being positioned to cooperate with a cam roll 32 carried by a driving arm or stud 83 formed upon a sleeve 3a, which is fixed to the shaft 16 and is rotatable therewith. In a. similar manner the cam surface '31 of the disk 31 is positioned to cooperate with a cam roll 35 mounted upon a driving arm 36 also fixed to The relative position of the disks 30 and 31 and the cam rolls 32 and 35 is shown in Fig. i) the cam roll 32 being shown in driving engagement with a projection 30 formed at the end of the cam surface 36 of the disk 30 and thus being e'liective to rotate the worm 15in the direction of the arrow at. It will he'understood that the cam rolls 32 and 35 may upon 'occasion be omitted, the driving arms then directly engaging the cam surfaces 30* and 31. v

- Having described the construction of my improved :reversing mechanism 1 will now describe the operation thereof. Taking the parts in the positions shown in Figs. 1 and 3 and moving in the direction of the arrows in said figures, let it be assumed that the direction of rotation of the driving shafi 16 is abruptly reversed. Previous to reversal, the cam roll 32 has been in driving engagement with the projection 30 upon the cam disk 30, the two disks and the intervening worm being thereby forced to the right uutilthe cam roll engages t 1?, cam surface 31 at the narrowest portion of the disk 31, thereby preventing further movement in that direction. As previously described, the

ng connection between the clutch coland the shaft 16 permits a consideramount of lost motion between the collar and shaft. During the reversal of the clutch collar and its lost motion relative to theshaft 15, the table, worm wheel and issues? worm will ordinarily come to res t in. order to prevent relative displacement of the driving arms and their associated cam disks" during this idle movement of the parts I provide the driving arms o3 and 36 with rounced extensions and 36 adapted to' frictionally engage spring arms 37 and 38 mounted upon the edges of the cams 30 and 31. and each positioned to engage one of the extensions and 36 and to thereby hold one of the rolls 32 or 35 in yielding engagement with one or the projections 30 or upon the cam disks. Displacement of the parts is thus prevented until the worm shaft 16, the roll will move away from 1 the front or driving side of the pro ection 1 30 and at the same time the roll 35 will move away from the rear side of a similar projection 31" upon the disk 31. This rela-- tive lost motion oi the driving cam-rolls away from the projections 30 and 31' per- I mits initial angular movement of tne shaft 16 iii the reverse direction without causing a corresponding reverse angular movement of: the worm 15. As the roll moves away from the rear side of projection 31' it engages the long wedge-shaped facefil 'ot the cam disk 31 and forcesthe disks and the intervening worm toward the left (as viewed. in Figs. 1 and During this operation the roll 32 is retreating from the cam surface 30. of the disk and thus interposes no resistance to the axial movement of the disks and also by varying the speed of revolution of the shaft 16. For example, the rate of angular increase may be so selected that the 4 worm l5 and the table actuated thereby will follow substantially the law of falling bodies in their acceleration. It will be evident that longitudinal movement of the worm 15 will necessarily move the periphery of the wheel 14: in the direction of axial travel of the worm and such movement of the worm wheel will in turn cause corresponding movement of the rack 11 and the table 10. The reverse movement of the table will thus be initiated without shock and with no positive engagement of driving mechanism. As the cam-roll 35 moves to the successive positions shown in dotted lines in 1 the longitudinal movement oi the worm 15 is, gradually accelerated, with a corresponding increase in the lllto of angular movement of the worm wheel 1%. It is my intention to so proportion the cam surfaces and 81 of the disks 30 and 31 that the worm wheel 14 cam roll 35 engages thedriving side of the projection 31 upon the cam disk 31. The worm will thereafter be revolved by the cam roll 35 as if it were rigidly secured to the shaft 16. As the worm wheel and table are already moving at their normal speed when the transition is made from axial to angular driving movement of the worm 15, there will be no change in velocity of table travel at this moment a d therefore no unusual strains will be tli rown upon the mechanism. The worm wheel? and table have been started from rest and brought up to. their normal speed by a gradual acceleration and the force necessary to cause such accelerationhas been permitted to act over the entire available time interval.

It will ble noted that the attainment of normal speed at the moment of positive driving engagementdepends solely upon the inclination of the cam face30 or 31, and that it does not depend upon the speed of rotation of the cams. It followsthat the cam surfaces. when properly proportioned for one speed in a given driving combination, are correct for all other speeds of the same combination, without alteration or adjustment. It may sometimes be desirable to allow a longer interval in which the table may be brought to rest. Under these conditions. I provide cam disks l0 as shown in Fig. 5, in which the portion l0 of the cam surface slopes'toward the left, as viewed in said figure, while the portion 40 slopes toward the right as in the cam shown in Fig. i. lVith this construction the table may continue its movement in the direction of previous travel for a short distance after the worm and disks have commenced their reverse rotation. After the cam roll reaches the low point of the cam, the table is gradually set in motion in the opposite direction, as previously described. Lost motion between the collar 27 and shaft lfiflis unneces' driving shaft 160 and slidable thereon between shoulders 51 and 52. The shaft 160 is mounted in bearings 170 and 180 as previouslydescribed, whereby endwise movement of the shaft is controlled. 'If thcparts are moving in the directions shown in Fig. l, the pressure of the worm against the worm wheel will force the sleeve 50 against the shoulder 51. lVhen forward rotation of the worm ceases. slight continued rotation of the wornrwheel due to the inertia of the table will slide the worm and sleeve along the shaft 160 until the sleeve engages the shoulder 52, against which it will be held by the pressure of the worm when driving in the reverse direction. The distance through which the sleeve is permitted to slide upon the shaft 160may be suitably related to the special conditions arising in any given machine. For the purposes of the claims it is to be considered immaterial whether the driving arms engage the disks directly or through the medium ofthe cam rolls.

Having thus described my invention it will be evident that other changes and modifications can be made therein by those skilled in the art without departing from the spirit and scope thereof as set forth in the claims, and I do not wish. to be otherwise limited to the details herein described, but

lVhat I claim is:

1. A reversing mechanism having, in combination, a driving shaft, means for rotating a worm mounted on said shift, a worm wheel meshing with said worm, and driving con nections between said shaft and worm etfect1ve to move said worm wheel after reversal at a,, gradually accelerating speed and to thereafter drive said worm Wheel positively at normal speed.

A reversing mechanism having, in com bination, a driving shaft. means for rotating saidshaft alternately in opposite directions, a worm mounted on said shaft, av worm wheel meshing with said worm, and driving connections between said shaft and worm effec- .tive to move said Worm wheel after reversal a worm mounted on said shaft and movable both angular-1y and axially relatively to said shaft, a worm wheel meshing with said worm, and means to give said worm, uponreversal of said shaft, an initial axial movement of gradually increasing velocity followed by a positive movement of rotation with said driving shaft.

4. A reversing mechanism having, in combination, a driving shaft, means for rotating said shaft alternately in opposite directions, a. worm mounted on said shaft and movable both angularly and axially relatively to said shaft, a worm wheel meshing with said worm, means to move said worm bodily endwise upon reversal of said shaft, thereby imparting a movement of rotation in the reverse direction tosaid worm wheel, and means to positively rotate said worm when the movement of said'worm wheel approximates its normal speed of rotation.

5. A reversing mechanism having, in cei bination, a driving shaft, means folr rotating said shaft alternately in oppcslte ,ilIIQCtl-GXIS,

a worm mountedon said shaft and movable a limited movement both axially and angu larly relatively to said shaft at each reversal thereof. i

A reversing mechanism having, in combination, a driving shaft, means for rotating said shaft alternately in opgosite directions, a w 'm inounted on said shaft and movable both ai'i gularly and axially r 'latively to said shaft, a Worm wheel meal ing with said worm, and driving connecti ns between said shaft and said worm, said onnections comprising reversibly-disposed cam disks secured to the opposite ends of said worm and apair of driving arms fixed to said shaft and each positioned tocooperate with one of said cam disks for driving'said worm.

7 A reversing mechanism having, in combination, a driving shaft, means for rotating said shaft alternately in opposite directions, a worm mounted on said shaft and movable both angularly and axially relatively to said shaft, a worm wheel meshing with said worm, and driving connections between said shaft and said WOIHI', said connections comprising reversibly-disposed cam disks secured to the opposite ends of said worm, and a pair of driving arms fixed to said shaft in spaced relation thereon andeach positioned to cooperate with one of said disks to drive said Worm in one direction. 8. A reversing mechanism having,in combination, a drivlng shaft, means for rotating said shaft alternately in opposite directions,

insane? a worm mounted on said shaft and movable both angularly and axially relatively to said shaft, a. worm wheel meshing with said worm, and driving connections between said shaft and said Worm effective to rotate said worm wheel by direct axial movement of said worm at the beginning of each reverse movement of said worm wheel and-to there after continue said rotation in the same direction by rotation of said worm.

9. A reversing mechanism having, in com bination, a driving shaft, means for rotating said' shaft alternately in opposite directions, a worm mounted on said shaft and movable both angularly and axially relatively to said shaft, a worm wheel meshing with said worm, driving connections between said shaft and said worm, said. connections including a cam and a driving arm at each end of said sleeve, a worm wheel meshing with said 7 5 worm, and driving connections between said sleeve and said worm, said connections comprising rcversibly-disposed cam disks secured to the opposite ends of said worm and a pair of driving arms fixed to said sleeve and each positioned to cobperate with one of said cam disks for driving said worm.

In testimony whereof I. have hereunto set my hand.

err/anions n. non'ron. 

